Only thing that catches my eye is, only 16GB ram for 300TB storage?
You don't need 10GbE and Cat6 for that. 1GbE and Cat5/5+ are fine. The SOHO NAS from Synology or QNAP with ARM CPUs, 1-2 GB RAM and 1x 1GbE ports are achieving such performance.
Anything worth using as a file server should have no trouble doing 100MB/sec with pretty much any protocol.
Yes, there were small bugs in the past, like waiting for some timeout when browsing shares on the server when the auth is done via Kerberos, but they were ultimately fixed.
I guess now that clients can't attach, it's technically in the warm-down phase of its workout.
Doesn't surprise me.